Abstract: The development of 5G communication system towards miniaturization, integration, low-power consumption and high performance requires higher performance and smaller size of 5G filter. The prototype circuit of Chebyshev Ⅱ bandpass filter is transformed to reduce the insertion loss and introduce two transmission zeros at the low frequency end; Two transmission zeros are introduced into the high frequency terminal by using parasitic parameters of the components through reasonable spatial layout and impedance matching optimization of the connecting ports of the components. From the two directions of circuit principle and three-dimensional structure, high stopband suppression and smaller in-band loss are achieved in small size. The GaAs substrate chip filter is designed and machined. The test results show that the simulation results are consistent with the test results, and the filter size is only 1. 0 mm×0. 8 mm×0. 1 mm.